This invention relates to a method of uniting a number of optical fibers into a bundle.
An optical fiber bundle has been widely used for transmitting illumination light in an endoscope. The optical fiber bundle is obtained by uniting or Joining at least opposites ends of a number of optical fibers. Generally, tubular members have conventionally been used for this uniting operation. More specifically, the end portions of a number of optical fibers to which an adhesive has been applied are inserted into the tubular members, and the optical fibers are united together upon solidification of the adhesive. It is preferred that as many optical fibers as possible be inserted into the tubular member so as to increase the density of filling of the optical fibers. In the above method, however, when trying to insert as many optical fibers as possible into the tubular member, the optical fibers are rubbed by the inner surface of the tubular member, and are damaged. Therefore, to increase the density of filling of the optical fibers has been limited.
Japanese Laid-Open Utility Model Application No. 59-43903 discloses a method of uniting optical fibers together, in which a number of optical fibers are first inserted into a tubular member of a circular cross-section, and then a wedge member is inserted into the tubular member, thereby increasing the density of filling of the optical fibers. However, when the wedge member is inserted into the tubular member, the wedge member rubs the optical fibers, and therefore may damage them.
In some cases, optical fibers in a bent condition are united together. For example, Japanese Laid-Open Patent Application No. 59-34239 shows in FIG. 5 a front end structure of an endoscope of a side-viewing type. End portions of optical fibers are bent generally right-angularly or perpendicularly, and in this condition they are united together by a uniting member. Although not described in detail in this publication, this uniting member is composed of two halves, and a pair of curved grooves are formed respectively in opposed surfaces of the two halves. The optical fibers are received in these grooves, and the two halves are connected together, with the two grooves mated together, thereby uniting the optical fibers. In this uniting method, the density of filling of the optical fiber is low, and the uniting operation is quite cumbersome.
A pamphlet "KSM alloy", published by Kanto Tokushuko K. K, discloses a joint for connecting two pipes together. This joint has a tubular shape, and is made of a shape memory alloy. Opposed ends of the two pipes are inserted respectively into the opposite end portions of the Joint, and then heat is applied to the joint to return it to its memorized configuration, that is, a smaller diameter, thereby connecting the two pipes together.